Difference in 1998 engine

I'm looking to replace a 1998 3.0L (Vulcan) engine. The online searches show a difference between whether the production date was before or after 7/13/98. Anyone what the difference in the motors would be? This is not going to the Duratec but staying in the Vulcan line.
Thanks.

There should be a barcoded label on the passenger side of your engine that will have the build date.

There are some gasket differences.
That's about it